During the election campaign, Sedgemore resigned from Labour and joined the Liberal Democrats[4] in protest at the attack on Iraq. Hillier retained the safe seat with a majority of more than 10,000 votes. She made her maiden speech on 24 May 2005, noting there were more men in the House of Commons that day than there had ever been women MPs.[5]

During maternity leave beginning in March 2009, her ministerial role was taken over by Shahid Malik. In March 2008, Hillier voted with the Government in favour of nationwide Post Office closures, including seven in Hackney, of which her constituency forms a part.[6]